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Chapter 12
Work and Machines
Term | Definition |
---|---|
work | force exerted on an object that causes it to move |
joule | unit of work equal to one newton-meter |
power | the rate at which one form of energy is transferred into another object |
machine | a device that changes the amount of force exerted, the distance over which a force is exerted, or the direction in which the force is exerted |
input force | the force exerted on a machine |
output force | the force exerted on an object by a machine |
input work | the work done on a machine as the input force acts through the input distance |
output work | the work done by a machine as the output force acts through the output distance |
mechanical advantage | the number of times a machine increases a force exerted on it |
efficiency | the percentage of the input work that is converted to output work |
inclined plane | a simple machine that is a flat, sloped surface |
wedge | a simple machine that is an inclined plane that moves |
screw | a simple machine that is an inclined plane wrapped around a central cylinder to form a spiral |
lever | a simple machine that consists of a rigid bar that pivots about a fixed point |
fulcrum | the fixed point around which a lever pivots |
wheel and axle | a simple machine that consists of two attached circular or cylindrical objects that rotate about a common axis, each one with a different radius |
pulley | a simple machine that consists of a grooved wheel with a rope or cable wrapped around it |
compound machine | a device that combines two or more simple machines |